The present invention relates to an electrode for alkaline storage batteries that uses a hydrogen storage alloy capable of electrochemically absorbing and desorbing hydrogen in a reversible manner as an active material.
Electrodes using a hydrogen storage alloy which can reversibly absorb and desorb hydrogen as the active material are large in theoretical capacity density compared to a cadmium electrode, and are free from deformation and dendrite formation unlike a zinc electrode. Such electrodes are promising as a negative electrode for alkaline storage batteries that affords a long life and ensures a high energy density, while keeping off pollution.
Common methods for producing those alloys for use in such hydrogen storage alloy electrodes include an arc melting method and an induction melting method.
Currently used hydrogen storage alloys for electrodes include La-- or Mm--Ni system multi-element alloys of AB.sub.5 type, where Mm represents a misch metal, i.e., a mixture of rare earth elements; A represents an element, such as La, Zr, Ti or the like, which is high in affinity for hydrogen, and B represents an element such as transition elements, for example, Ni, Mn, Cr and the like, which is low in affinity for hydrogen. When those multi-element alloys are used in a battery, they exhibit a capacity close to their theoretical value, and thus it is impossible to expect a further drastically increased capacity for these alloys. This is why there exists a demand for an innovated hydrogen storage alloy material which affords a larger discharge capacity than the conventional alloys of AB.sub.5 type.
Alloys that are larger in capacity to absorb hydrogen than those of AB.sub.5 type include Ti--V system hydrogen storage alloys. There are proposals to use alloys of this system, for example, those represented by the general formula Ti.sub.x V.sub.y Ni.sub.z for the hydrogen storage alloy electrode (Japanese Laid-Open Patent Publications Hei 6-228699, Hei 7-268513, Hei 7-268514, etc.).
Although electrodes prepared from the Ti--V--Ni system hydrogen storage alloys have a larger discharge capacity than the La-- or Mm--Ni system multi-element alloys, they have some problem in their cycle life characteristic.